Idea

In philosophy, an idea is a mental representational image of an object, as well as abstract concepts that do not present as mental images. The ability to create and understand the meaning of ideas is considered to be an essential and defining feature of human beings.

Divine Illumination
There have been a few main theories concerning the source and origin of our ideas. Augustine of Hippo argued for the "divine illumination of the intellect", a notion that dated back to antiquity. The process of human thought needs be aided by some sort of supernatural assistance; by "divine grace" in Christian parlance. It is an alternative to naturalism in epistemology, and it was an important theory for both neo-Platonism and Augustinianism. Socrates said in the Apology that infants have inner voices that suggest to not do something potentially harmful, and Socrates argued that an invisible spirit gave these suggestions. About 750 years later, Augustine emphasized divine illumination in our thought, without which humans would be incapable of reasoning. Augustine said that the mind needs to be enlightened from a mind from outside in order to find truth, and that, "You have heard nothing true from me which you have not told me." Minds need an intelligible light from God in order to know, especially in regard to knowing eternal truths that are greater than the mind itself. Augustine's theory was defended by Christian philosophers during the Middle Ages, including Franciscans such as Bonaventure.

Criticism
The doctrine of divine illumination had its critics, including Thomas Aquinas, who denied that, in this life, we have divine ideas as an object of thought, and that divine illumination is sufficient on its own. He also argued against the notion of continuing divine influence on human thought, believing that people have the capacity to think for themselves. Aquinas was a proponent of the notion that intellectual knowledge is the result of the abstraction of general ideas from the images that are imprinted in our minds from sensory data.

Defenders
After Aquinas, a principled defender of divine illumination was Henry of Ghent. Henry argued against Aquinas, saying that our knowledge must be assisted by divine illumination. He believed that ideas can be compared with a created exemplar, which we have in the soul, and an eternal exemplar outside of the soul. No comparison to a created exemplar can give us infallible truth, and divine illumination supplies infallible truth. Henry's defense of divine illumination was attacked by another supporter of the theory, Duns Scotus, who believed that Henry's defense would lead to skepticism.

Active/Agent Intellect
Active/agent intellect is a concept in both classical and medieval philosophy that is connected to the theory of hylomorphism, referring to the formal aspect of intellectual knowledge. The nature of the active intellect was a subject of intense discussion, especially in medieval philosophy, with Muslim, Jewish, and Christians seeking to reconcile Aristotle's "body and soul" with their own religions. Aristotle's On the Soul contains the idea of the active intellect, in which he held that matter is potentiality, and that it is necessary in the soul, too, that the distinct aspects of the potentiality of matter and the productive thing (by which things are formed) are present.

Aristotle made the case of two intellects: passive (latent capacity) and active (which activates the latent capacity). The passive intellect is the material thought, while the active intellect is the active principle which forms thought and activates the passive intellect. He drew a comparison with light's formation of impotent colors and the intellect in the mind, saying that they both make potential things what they are. As well as being without attributes and unmixed, the active is always greater than the passive, as a governing source is above the material that it works on. Epistome (intellectual and rational knowledge) is in its being at work (in its potential) is the same as the thing it knows, as it does not take precedence in time. This does not mean that it occasionally thinks; the active intellect is always at work. When it is separated, it is active thought, and the active intellect is eternal and everlasting. Aristotle's view of a human afterlife was knowledge surviving death, but our personal identity does not survive death. Aristotle infers that there is some form of activity, and that the distinction between capacity and activity must exist in the soul as well. He later equates the active intellect with God, a theory in both ancient times and the Middle Ages. People have debated Aristotle's intentions for years, especially whether it is a part of the soul, or from God.

The three positions concerning active intellect are Aristotle's correlation of active intellect with his stance in his Book Twelve of his Metaphysics (active intellect is God); the case that it is not God, but is still the same for all humans, and that it is spiritual intelligence in between God and mankind; and Aquinas' theory that the active intellect is a faculty of each human soul.

Middle Ages
Early Greek commentators of Aristotle regarded the active intellect as a power external to the human mind, with Alexander of Aphrodisius equating it with God. However, others believed that it was external to the human mind, but was instead a form of intelligence, not God. Along with Neoplatonic views, these philosophies influenced the development of Arabic philosophy, which was later commented upon by Latin philosophers.

The Muslim philosopher Avicenna and the Jewish philosopher Maimonides believed that the active intellect was external to the human mind, and that it was a being independent of man. Their position was that it was the lowest of the ten eminences/intelligences descending through the heavenly spheres. Maimonides believes that prophecy is a revelation from the divine being through man's active intellect. More strictly Aristotelian thinkers such as Averroes believed in the "conjunction of the intellect", the view that philosophers could conjoin their potential intellect with the active intellect and achieve a state of philosophical nirvana. Muslim and Jewish Aristotelians posited a single external active intellect due to their beliefs that all rational beings posess, or can access, a fixed state of concepts; a unified, correct knowledge of the universe. The only way that all human minds posess the same correct knowledge is if they can all have access to central knowledge, the "mind of the universe", which makes all other thought processes possible.

In Medieval Europe, Siger of Brabant agreed with Averroes on every point. Thomas Aquinas, however, argued against the Averroist position, claiming that the active intellect is part of the individual human personality, distinct faculties of the soul. An obscure school, appealing to Alexander of Aphrodisius, rejected linking the active intellect to the immortality of the soul. It was viewed as a force triggering intellection in the human mind, causing thoughts to pass from potentiality to actuality. That force was argued either be external to the soul or is a faculty of the soul. The agent intellect must not be confused with the "intellect in act", the result of the triggering done by the agent intellect. Agent intellect is closer to the psychological term "active knowledge", while a person's cumulated knowledge can be one's "acquired intellect".

Innatism
Innatism is the notion of the existence of innate ideas. In both philosophy and psychology, it is a concept or knowledge said to be universal to all humanity; something that all people are born with, rather than learning through experience. Innatism is controversial, as it is an aspect of a long-running nature vs. nurture debate regarding human nature. The theory has its origins in Plato, who argues that, if there are certain concepts that we know are true without experience, we have a pre-natal, innate knowledge of things.

Since Plato, there has been a long-running philosophical debate concerning innate ideas, which was later a debate between John Locke and Gottfried Wilhelm Leibniz. Innate ideas are said to belong to a fundamental level of human cognition. Rene Descartes believed that knowledge of God is innate in everyone, while empiricists such as Locke, George Berkeley, and David Hume believed that human knowledge is obtained through sensory experience, not through a priori reasoning. Immanuel Kant ended the impasse between the rationalists and empiricists by synthesizing the two views, although his success in doing so has been debated.

For Descartes, innate knowledge and ideas is something inborn, and that something that is innate is effectively present from birth (although it might not reveal itself then). Descartes' comparison of innate knowledge to an innate disease, which may show up later in life, suggests that, if another event prevents the disease/knowledge from occurring, the knowledge still exists, despite not having been expressed. Leibniz suggested that we are born with certain innate ideas, such as mathematical truisms such as 1+1=2, which does not require empirical evidence. Empirical evidence can only show us that concepts are true in the present, not in the whole of history. Leibniz called these mathematical truisms "necessary truths." Another example is "What is, is," and "It is impossible for a thing to be and not to be" (the Principle of Non-Contradiction).

Leibniz argued that such truisms are universally asserted, and that they are acknowledged by all to be true; it must be due to their status as innate ideas. Empirical evidence can serve to bring to the surface some innate principles, serving as a catalyst. He compared this to needing to hear only the first few notes to recall the melody of a song.

The main antagonist of innate ideas was John Locke, who argued that the mind is a tabula rasa (blank slate) at birth, and that all ideas are constructed in the mind through constant composition and decomposition. In his essay Concerning Human Understanding, he argues that universal assent proves nothing, apart from that there is universal assent. Even a phrase such as "What is, is" is not always agreed upon, as infants and old people might not be able to have the ability to think about it. Locke also said that humans can be aware of the fact that they already knew the melody to the song, and that hearing the first few notes would confirm this. The same knowledge regarded as a priori according to Leibniz is actually a posteriori knowledge, which has been lost or forgotten by the unaware person.

Scientific ideas
Plato raised an important epistemological quandry in reasoning about the validity of knowledge, questioning how humans have ideas that are not conclusively derivable from our environments. Noam Chomsky took up this issue, seeing the problem as a philosophical framework for the scientific inquiry into innatism, and he believed that his linguistic theories had an answer. Our linguistic systems contain systemic complexity which supposedly could not be empirically derived. Essentially, human's accurate grammatical knowledge cannot be gained through experience; humans are born with innate grammar, enabling the language learner to categorize language into a system. The ability to construct and judge sentences is gained from innate knowledge, and Chomsky believes that language provides a window into the human mind. If this is so, at least a part of human knowledge consists of cognitivity, and that it is gained from the mind itself, not solely through experiences; at least some of that information must be innate.